Reinforced-concrete floor construction



W. M. PRATT. REINFORCED CONCRETE FLOOR CONSTRUCTION. APPLICATION man NOV. 12. 1911.

1,340,291. Patented May 18, 1920.

WALTER M. PRATT, O F DETROIT, MICHIGAN.

REINFORCED-CONCRETE FLOOR CONSTRUCTION.

Specification of Letters Patent. Patented luaty 1S, 1920.

Application filed November 12, 1917. Serial No. 201,428.

To all whom it may concern:

Be it known that I, WALTER M. PRATT, a citizen of the United States, residing at Detroit, in the county of Wayne and State of Michigan, have invented a new and useful Reinforced-Concrete Floor Construction, of which the following is a specification.

This invention relates to a reinforced concrete fioor construction, and consists in the novel relation between a floor slab and certian supporting members, as hereinafter specifically described. v

The object of the invention is to prov de a floor construction employing precast olsts having partially embedded therein bonding members which are also partially embedded in a floor slab supported by said joist, so that the slab reinforces and strengthens the joists, instead of figuring solely as a dead weight or load.

Other objects of the invention are to provide precast concrete joists having ceillng supporting means integrated therewith, and to provide for an anchorage connection between a reinforcement embedded in the slab and certain members bonding the slab to the joists.

These objects are attained by the construction illustrated in the accompanying draw ings, wherein:

Figure 1 is a perspective view of a portion of a concrete floor embodying the primary features of the present invention, omitting the fioor slab sufliciently to disclose the nature of the foundation on which said slab is poured and the bonding members which.

are integrated with and project above the joists.

Fig. 2 is a perspective View of a concrete floor foundation, somewhat modified from the construction shown in Fig. 1, both with respect to the joists themselves and the members extended between the same.

Fig. 3 is a perspective detail view, showing adjacent portions of a slab and supporting joist and a member for bonding the same differing from those disclosed in Figs. 1

and 2. I

Fig. 4 is a perspective detail view of still another type of bonding member cast into a joist.

Fig.5 illustrates in perspective a modification of the invention, wherein the joists are arranged closely adjacent.

Figs. 6 and T are sectional views of another modification, in which the joists are of square cross-section and partially hollow instead of T-shaped, as in the other forms of the invention.

Referring now more in detail to that form of the invention shown in Fig. l, the reference character 1 designates a plurality of parallel, spaced, T-shaped concrete joists,

by marginally depressingthe top surfaces of the joists, the plates and slabs thus being made flush. Said joists and plates jointly form a foundation for a concrete slab 5, which is suitably reinforced as by the Wire screen or netting indicated at 6. Upon the slab proper there may be superposed one or more of such finishing layers as isindicated at 5 in said figure.

The slab is securely bonded to the joists for the purpose of adding thereto its own shearing strength, and it is preferred to perform this function conjointly by a number of different bonding members such as are indicated respectively at '7, 8, 9, and 10. The members 7 are hollow blocks, preferably metallic, which are spaced longitudinally of the joists, and have their lower portions embedded therein while their upper portions are adapted to be embedded in the slab. By reversely flaring theupper and lower portions of said members 7, the anchorage effect is increased, this effect being added to also by the openings ll which are extended Vertically through said members. The members 8 are bars which are extended zig-zag in a substantially vertical plane through the center portions of the joists, thus reinforcing the same, and 'which have their angular upper portions projecting above the joists so that they may embed themselves in the slab. The members 9, of which the detail arrangement is best shown in Fig. 5, are rods which are embedded in the joists at intervals and lie substantially in planes transverse thereof, said rods forming reinforcing loops respectively in the horizontal and vertical portions of the joists and having end portions which are extended laterally in opposite directions above the joists to be embedded in the slab. The members 10 are spikes which are embedded at intervals, heads down, in the top portion of the joists, the shank portions of said spikes being allowed to project for engagement in the slab, and a number of the portions thus projecting being bent down upon the netting 6. It will be noted that the angular lower portions of the zig zag member 8 form stirrups wherein one or more of the reinforcing rods 2 is supported. For somepurposes it Wlll be desirable tov conceal the joists by arranging ceiling boards 12 beneath the same, and as a supporting means for such boards spikes 13 may be embedded in the lower portions of the joists with their shanks projecting therebeneath to engage said boards as Fig. 1 shows.

In the modified construction shown in Fig.

D 2, the T-shaped joists 14 have partially embedded therein a series of spaced members 15 having the form of chain links, the upper portions of saidmembers being exposed above the joists to be embedded in a floor slab (not shown). Through said members 15 there is passed one or more bars 16, ex-

tending longitudinally of the joists, 'thereabove, and a series of bars 17 extending transversely above the joists are looped about the bars 16 as is indicated at 18.1 The bars 16 and 1 7 constitute reinforcements for the slab, and thelatterbars function further as supports for plates 19 of expanded sheetrmetal which close the spaces between the joists, coacting with the same to form a foundation for the slab. As a provision for supporting a ceiling from the joists lat said joists are ribbed at each side of their demembers, the top face of the joist is depressed at one or both sides of said members, as indicated at 25, the length of said depressions being, however, less than that of the members 23 so that the latter will compensate for any tendency of the former to weaken the shear resistance of the joist.-

In the construction shown in Fig. 4, a T- shaped concrete joist 26 has embedded in its top portion a concrete block 27, a flared portion ofwhich projects above the joist and is adapted to be embedded in a floor slab (not shown). To increase the bonding effect of said member, it is'preferred to form in the top surface thereof transversely intersecting grooves 28 having undercut walls, and the portion of said block within the joist may be given increased retention by forming therein one or more horizontally extended openings 29. A number of smaller openings 30 will also extend horizontally through the block to receive the 'rods 31 which reinforce the joist, the blocks thus constituting positioning members for said rods.

In Fig. '5 there is shown an arrangement of two T-shaped concrete oists in close proximity thus adapting them to support a coilsiderably greater load than the spaced joists shown inFigs. 1 and 2.

,In theconstruction illustrated in Figs. 6 and 7, there are employed. rectangular reinforced concrete joists 32 which are shown as having their corresponding ends supported upon .a wall or column 33. Owing to the concentration'of stresses in the portions of the joist lying in the region of maximum shear, adjacent the member 33, said portions are made solid, but the portions outside of said region may be made hollow, as is indicatedat 34:. While these joists are shown as closely adjacent, it will be understood thatlthe spaced relation may vary according to theload andother controlling'conditions. Said joists are reinforced by rods 35 extending longitudinally and are further reinforced at intervals by transversely positioned'looped rods 36, the end portions of which are transversely extended in opposite "directions above the joists and embedded in a floor slab 37 supportedby the joists, U i

It is to be observed-that the above-described construction is such as to allow the joists in all their modified forms to be precast and made availablein a variety-of standard lengths and cross' sections, the bonding'mem'bers being integrated with the joists when the latter are formed. Thus there may be eliminated much labor dur ng the actual floor construction, and a considerable saving oftlme' effected as compared with casting the joists in their positions of" i use which is the followed.

By bonding theslab to the joists as in the construction above-described, the resistance of. a floor to longitudinal shear is very materially increased, since the shearing strength of the slab is thus added to the joists, whereas" without such bonding provision, an excessive load upon the floor, would buckle the slab prior to shearing of the joists, so that the strength of the slab would be entirely ineffective in resisting such a load.

hat claim is:

practice now commonly 1. In a reinforced concrete floor, a con- 'crete joist, a slab supported by said joist,

members spaced longitudinally of the joist embedded jointly therein and in the slab, and a Zig-zag 'bar embedded in the joist and having a series of projecting portions embedded in the slab, and bonding the same to the joist.

2. In a reinforced concrete floor, a T- shaped concrete joist, a slab supported by said joist, a zig-zag bar embedded in the joist and having a series of projecting portions embedded in the slab, and supplemental reinforcements arranged at intervals along the joist and rods looped in the horizontal and vertical portions of the joist having end portions 10 laterally extended within the slab.

respectively comprising 3. In a concrete floor construction, the combination with a T-shaped concrete joist, of a slab supported thereupon, and a series of members spaced longitudinally joist, anchored thereto throughout substantially the entire width thereof, and embed- (led ,in the slab, to add the shearing strength thereof to that of the joist.

WALTER M. PRATT.

of said 

